How can I keep my whole music library on my NAS and comfortably access it and manage it there and at the same time have a music selection locally stored on my MacBook that I can manage while away and that gets synchronized with my NAS library when I get back.

Is there way to do that?

My Setup: a Synology DS412+ with DSM 4.1 and a MacBook Pro with Mountain Lion

Update:
The idea is to have a master library on the nas and a slave library for mobile use that merges all changes back to the master and gets updated information from the nas. Like a selective cloud sync.

Update (2):
The purpose of this usage is to be able to play music without having access to broadband internet (train, plane, car, public places, ...) without maintaining two libraries.

5 Answers
5

You could set up something like this (Make sure that your iTunes Library File (iTunes Music Library.xml) is on your mac, not on your NAS):

Create a playlist "On the go"

Use this script to move the files in the playlist from your NAS (iTunes media location) to your mac.

On the go, with no connection to your NAS: iTunes will tell you that the files are not available when you click to play, click "search" and select the folder you´ve synced the files to.

When you add new music on the go, iTunes will copy that to the default location (/music/iTunes/) on your mac.

When you have access to your NAS again: Check that the iTunes Media Location is your NAS (Settings > advanced) and click File > Media Library > Organise Media Library. All Files you added while on the go will be copied to your NAS.

I am not totally sure that this would work since I don't have your hardware (my home server is an old G4 - works like a charm), but here goes. According to the official documentation on Synology's site, you can easily run iTunes server using their software. If the screenshots, etc., are correct and accurate indicators of the function, you should be easily able to accomplish what you're after using that and the standard sync software they provide. If you haven't set up iTunes server yet, do that. If you have, keep the iTunes media folder on the NAS current using the rest of the sync software. You may have to restart the iTunes server to have it "see" the new files, but it should do the trick.

Note: there is the "Automatically Add to iTunes" folder at ~/Music/iTunes/iTunes Music/ that you might try to monkey with; however, I don't know if such a folder exists on their server version and I have had limited success using this on my local setup. Sometimes she work, sometimes she no work.

I had an iTunes Server but it only shows as a list of songs. No Album, Artist or Genre View. Also, it's not possible to edit the song information (adding covers or editing tags). Thx for the answer though.
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soeluOct 8 '12 at 22:37

More general thought regarding NAS usage:It kinda defeat the purpose of a NAS if you have to maintain a local library. Imo, having the NAS always connected and an internet connection at disposal to access it when you're away, are the 2 constraints to satisfy to take advantage of a such device.

but how will information get synced between those libraries? this is the solution I'm using now and that I'm unhappy with.
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soeluOct 9 '12 at 7:29

can you be more specific about the info you want synced ? is it just id3 tags or iTunes related like ratings or playcounts?
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kraymerOct 9 '12 at 7:39

preferably every but mostly tags and new songs. The idea is to have a master library on the nas and a slave library for mobile use that merges all changes back to the master and gets updated information from the nas. Like a selective cloud sync. (added this to question body)
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soeluOct 9 '12 at 7:59

The purpose of this usage is to be able to play music without having access to broadband internet (train, plane, car, public places, ...) without maintaining two libraries. The issue would not occur when we would be talking about a desktop computer.
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soeluOct 9 '12 at 9:37

Just to be sure: you don't have an iOS device? because an iTunes synchronisation would work a treat
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kraymerOct 10 '12 at 8:45

If your library has fewer than 25,000 tracks, this is the perfect use for iTunes Match. You will see all the music in the laptop's library, but you can download only what you want on that computer. You download what you want when you're on wifi. Anything you add to the laptop will get synced to the cloud, and you can download it on your main Mac.